1. Field of Invention
The present invention relates to a power metal-oxide-semiconductor field effect transistor (MOSFET), and more generally to a power MOSFET with improved breakdown voltage.
2. Description of Related Art
Power MOSFETs are mainly applied to power switching devices. For example, a power MOSFET serving as a power on/off switch is provided in various power management apparatuses.
Generally, in order to maintain the breakdown voltage in the termination area 100 around devices in the active area of a power MOSFET, a plurality of floating trench rings 102 is disposed within the termination area 100, as shown in FIG. 1. Similar concepts have been disclosed in U.S. Pat. No. 6,462,379 and U.S. publication number 2008/0179662.
However, as the level of integration for power MOSFETs continues to increase, the dimension thereof is accordingly decreased. Therefore, how to maintain or even increase the original breakdown voltage when the device is scaled down has become one of the main topics in the industry.